Luminescence of Impurity Ce3+ Centers in KH2PO4 : Ce Crystals

The photoluminescence, X-ray luminescence, and cathodoluminescence spectra of KH2PO4 : Ce single crystals contain a nonelementary band of radiation with an energy of 3.55 eV and decay time of 27-33 ns. It is formed by fast radiative interconfiguration d -> f transitions between the excited and ground states of Ce3+ ions, with the ground state is split by a crystalline field. In the range of concentrations studied (0.5-3 x 10(-2) wt %), Ce3+ ions enter the KH2PO4 : Ce crystal lattice as substitution ions. Local charge compensation takes place by means of defects in the crystal structure that cause luminescence with a large Stokes shift in the region of 2.4-2.2 eV. The presence of hydrogen sublattice defects decreases the efficiency of energy transport by free charge carriers to the luminescent centers. The interaction of defects and impurity centers manifests itself as a slow inertial building-up of the stationary X-ray luminescence yield of Ce3+ centers.